regarding: instance of 'std::bad_alloc' - c++

Question

I read other posts but none of them helping at all,
This code have no error still there is bad_alloc error...
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
char super[25];
char name[25],last_name[25];
int length;
char *sym = "#";
char *buffer;
ofstream outfile;
outfile.open("farses.dat",ios::app);
cout << "Writing to the file" << endl;
cout << "Enter your First Name: ";
cin >> name;
outfile << *sym;
outfile << name << endl;
cout << "Enter your Last Name: ";
cin >> last_name;
outfile << *sym;
outfile << last_name << endl;
cout << "Enter The Sentence : ";
cin.getline(super,25);
outfile << super << endl;
outfile.close();
ifstream infile;
infile.open("frases.dat");
infile.seekg(0, ios::end);
length = infile.tellg();
infile.seekg(0,ios::beg);
buffer = new char[length];
infile.read(buffer , length);
cout << "\n\nReading from file \n\n" << endl;
cout << buffer << endl;
infile.close();
return 0;
}
This code is terminating after coming to sentence statement..the getline() function is causing problem i guess but when i tried on other two statements(name and last_name),the getline(), it works perfectly..i even degraded the char limit to 5 too but after sentence statement is throw anyways

Answer 1

Thumb rule, don't fool yourself into thinking that your code has no errors. Especially when you clearly got an error. This kind of mindset will make you unable to find errors because everything you see is correct.
You never checked if your streams were open and you entered the wrong file name in the ofstream.
What happens is that, you write your data into a file name farses.dat and then you try to open a file called frases.dat (which I assume is the correct name, it means sentences).
You are getting the cursor position ifstream::tellg of an inexistent file, and it fails so the function returns -1. This is the value of length before you allocate your buffer.
When you do allocate your buffer you get a bad_alloc exception (bad_array_new_length).
Checking if your file was open would, at the very least, have saved you some debug time.
Something like this,
ifstream infile;
infile.open("frases.dat");
if ( infile.is_open() ) {
// File is open, do stuff (...)
if ( length <= 0 ) {
// Empty file / error, don't create buffer!!!
}
// (...)
infile.close();
}
else {
// Couldn't open file
}
EDIT: Fixed error explanation.